Good analysis!

However, you appear to assume that the evolution of the Watchtower movement will be steady and gradual. I don't disagree that this is one way in which matters could play out. Nevertheless, I think there is a good possibility of a tipping-point, game-changing event down the road that could figuratively blow things up. Before you think I'm being unrealistic, allow me to explain.
If we postulate (and I do) that the governing body members believe in the Watchtower organization whole-heartedly, as opposed to being cynical manipulators, let's try to put ourselves in their shoes. Each is clearly more delusional than your average member, as evidenced by their claiming to be anointed despite the strong institutional pressure against such claim. Moreover, they've invested their lives into this belief system. It is becoming quite clear that the current JW belief system has failed. What would we do if we were governing body members? We could keep pretending like nothing's changed, keep repeating the same ol' "the end is right around the corner" mantra, or we could do what the Bible Students did when 1914 didn't pan out: re-invent the religion in significant ways.
Big, significant changes are harder to bring about in Watchtower today because of its rule-by-committee structure. From what we know, 2/3 of the GB must agree on any changes to traditional policies. But, what if you have several strong personalities on the GB who start believing that Jehovah is personally using them to correct something or another in the organization? We can easily see how the seeds of discord can be planted and could potentially lead to power struggles at the highest levels of the organization. If you combine that with an already-weakening faith of the membership in the Western world, and perhaps a decline in membership/donations that serves to create a quasi-panic situation, it's not hard to envision a scenario where significant changes are brought about in the Watchtower organization in a fairly short period of time, perhaps along the lines of what happened at the World Wide Church of God.
Again, I'm not saying this scenario is any more likely than the more gradual scenario you described above. I'm just saying it's a possibility we should consider as well.